Thirty years after the great storm during which around 15 million trees were blown down, another event, potentially as significant, is affecting Britain’s ash tree population. Chalara fraxinea, commonly known as ash dieback, was first confirmed in the UK in 2012. The disease is caused by a fungus called hymenoscyphus fraxineus and is believed to have come here from Holland in young nursery ash plants and via airborne spores.
The disease can be identified by leaf loss, a dying off of a tree’s crown and bark lesions which render the tree more susceptible to infection from other pathogens. The disease can make wood more brittle and owners of roadside trees must be mindful of the potential hazard of falling branches.
There is currently no cure for the disease, but the Forest Research Agency, among other scientific research institutions, is looking at breeding disease resistant strains of ash tree as it has noticed that some trees seem to be able to tolerate or resist infection.
However, controlling the spread of the disease could be helped by regular thinning of trees to allow more air through the stands. You can help to slow the spread of the disease in parks and gardens by removing and disposing of infected ash plants, and collecting up and burning (where permitted), burying or composting the fallen leaves. This breaks the fungus's life cycle.
If you suspect a tree is infected report it to the Forestry Commission’s Tree Alert. More information is available from its website.